Because LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
FIG. 7 is a schematic, side cross-sectional view of a conventional LCD. The LCD 10 includes a TFT (thin film transistor) substrate 11, a color filter substrate 12, and a liquid crystal layer 13 interposed between the substrates 11, 12.
FIG. 8 shows an abbreviated circuit diagram of the TFT substrate 11. The TFT substrate 11 includes a plurality of rows of parallel scan lines G1, G2 . . . , and a plurality of columns of parallel data lines D1, D2, D3, D4 . . . orthogonal to the rows of parallel scan lines. The crossing scan lines and data lines define a plurality of pixel regions. Each of the pixel regions includes a pixel electrode 111 and a TFT 114. The TFT 114 is positioned near the crossing of a corresponding scan line and a corresponding data line. A gate electrode of the TFT 114 is electrically coupled to the scan line, and a source electrode of the TFT 114 is electrically coupled to the data line. Further, a drain electrode of the TFT 114 is electrically coupled to the corresponding pixel electrode 111.
FIG. 9 shows a top plan view of parts of the color filter substrate 12. The color filter substrate 12 includes a plurality of red, green, and blue color filter units 121, 122, 123, and a black matrix 125 filled in gaps between the color filter units 121, 122, 123. Each of the color filter units 121, 122, 123 corresponds to one of the pixel electrodes 111, and has an area equal to that of the corresponding pixel electrode 111.
In operation, voltage signals are provided to the pixel electrodes 111 via the data lines, so as to control the liquid crystal molecules of the liquid crystal layer 13 to twist to a pre-determined orientation. Thereby, an exactly quantity of light passing through the color filter units 121, 122, 123 is controlled. The white light beams are converted into red, green, or blue light beams after passing through the red, green, or blue color filter units 121, 122, 123, respectively. Thus, the red, green, and blue light beams with different brightness mix together, so as to display light beams of numerous different colors.
The light beams passing through the color filter 12 may be divided into several brightness levels, which are called gray scales. The more gray scales that are defined for the LCD 10, the higher the resolution of images that can be displayed on the LCD 10. In order for the LCD 10 to display different images, the gray scale of each of the pixel regions may change, whereby the liquid crystal molecules need to twist to a pre-determined orientation according to the variation of the gray scale. The twist speed of the liquid crystal molecules is proportional to the voltage signals applied thereto, which in turn are proportional to the voltage signals provided to the pixel electrodes 111. When the image of the LCD 10 changes from a white image to a black image, the voltage signals applied to the liquid crystal molecules are the largest, whereby the liquid crystal molecules undergo the largest change in twist orientation at the fastest twist speed. In addition, when the image displayed on the LCD 10 changes in a smaller range of the gray scale, the voltage signals applied to the liquid crystal molecules are smaller, whereby the liquid crystal molecules undergo smaller changes in twist orientation at slower twist speeds.
The LCD 10 often displays colored images, and the variations of the gray scale are usually relatively small, with the voltage signals applied to the liquid crystal molecules being correspondingly small. Therefore the liquid crystal molecules are liable to twist at low speeds, whereby the LCD 10 has a low response time.
It is desired to provide an LCD and method for driving the LCD which can overcome the above-described deficiencies.